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back to article CERN boffins re-running neutrino speed test

In the wake of September’s surprising experimental results that suggested the observation of faster-than-light neutrinos, CERN has announced that it has been re-running the experiment over recent days. Since the pre-publication release of its original dataset, CERN’s data has been raked over by physicists, scientists, computer …

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Boffin

Can anyone explain why the experiment doesn't use a fibre optic loop so that the neutrinos can be received by the same facility as send them out in the first place. This would reduce the complexity of the experiment removing time anomalies (or have I missed something in my naive knowledge of physics).

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Because it neutrinos, not photons.

I shouldn't take the piss tho. Its a good idea. But I don't think they have neutrino compatable reflectors.

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WTF?

ET

neutrinos pass through nearly any matter. Just looked it up and said even passes through planets, wtf

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Loop?

Can't be done. Neutrinos travel through ordinary matter such as glass without taking much notice of it; they don't obediently follow along a fibre like photons do. Most of the neutrinos that make it from CERN to Gran Sasso aren't detected, they just continue on their way; just a very few of them interact with the detector material and get recorded.

It's quite different from the original Michelson-Morley experiment that led Einstein to figure out relativity, where the photons were indeed reflected back.

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Boffin

Neutrinos != light

They would just pass straight through the fiber optic cable, and there's no good way of directing them which would allow you to send them in a circle (even the detectors are inefficient, since they interact so rarely with anything)

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Silver badge

I don't think you can persuade neutrinos to go round corners.

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Happy

Yes...

... neutrinos won't go round a fibre optic loop. In fact they pass through pretty much everything, which is why creating a neutrino detector is such hard work.

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Neutrino Physics 101

Because neutrinos hardly interact with matter, you can't steer them once they have been produced. The only way the experiment works is by putting the detector in line with the beam that is being produced. Then you have to work out which neutrinos MAY have come from the source (since the universe is filled with background, ....)

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Neutrinos only interact very weakly with matter and wouldn't follow an optical fibre.

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Stop

Neutrinos are not photons.

They act in ways different to light. The ones causing all the problems have been fired through 730km of rock, the chances of them following an optical fibre are, I would suggest, slim to none.

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Silver badge

Youve missed something

Nutrinos don't flow down a fiber optic cable the way light does. The problem with nutrinos is that they are so small the pass through allmost everything. Occasionally, where occasionally is a verry small number, one hits a sub atomic particle and can be detected.

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Alien

Sorry, but yes, you have. Neutrinos aren't affected by a wave guide such as a fibre optic cable. They stop for nothing and nobody. Their path is a geodesic. With only occasional exceptions they pass through matter as though it doesn't exist.

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Neutrino Physics 101

Because Neutrinos hardly interact with normal matter, they cannot be steered, you have to put the detector in line with the source.

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You can't send neutrinos through a fiber because they won't reflect on its walls. Neutrinos practically don't interact with matter, they go right through it.

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Anonymous Coward

The neutrinos are not being sent along a conduit, they are literally passing through the Earth to the detector, such is their nature. This site has a good explanation http://www.wired.com/geekdad/2011/09/neutrinos-and-the-speed-of-light-a-primer-on-the-cern-study/

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Neutrinos care not for earthly possessions

Neutrinos tend not to interact with matter, and anyway they're not photons so optical fibres would be unlikely to help even if they weren't so weakly interacting.

To give an idea of how weakly interacting there are, the solar neutrino flux at the distance of earth's orbit from the sun is on the order of 10^14/m²s, and it takes gigantic detectors built in deep underground caverns containing tens of thousands of tonnes of water to pick up even a handful of them each year.

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Simple answer, because you can't constrain neutrinos to a fibre optic cable, why would you be able to? Fibre optic isn't magic - it only works on photons, and only photons of certain energies at that.

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Because neutrinos could pass through the walls of your 'fibre-optic' cable (and maybe right through the middle of every planet in the solar system as well) without even breaking a sweat.

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Because a neutrino beam can't be bent.

Photons can be made to follow an optical fibre if the angle they make with the sides of the fibre is low enough for them to all be reflected back into the cable.

However, neutrinos are particles that barely interact with other particles enough to be detected, which is why they can travel 732 km through solid rock. The chances of reliably deflecting such a beam in a circle are approximately zero. Similarly, they carry no electric charge so magnets won't deflect them either.

To show how unreactive neutrinos are, Its been calculated that a neutrino beam can penetrate a lightyear of solid lead without loosing more than a few percent of its brightness and they can whistle through the sun almost without noticing that it was there.

So, as collisions don't deflect them, they can't be reflected by anything, and magnets or electric fields don't affect them, you have no choice except to design the experiment around measuring a straight beam on neutrinos.

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Mushroom

flogging a dead horse

18 responses and counting, all with minor variations on the theme "neutrinos pass thru anything and are hard to detect", without any non-topical interruptions - got to be an El Reg record. Sorry to break the chain, guys :-)

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Headmaster

Has any one said neutrinos won't follow a loop yet?

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Headmaster

Neutrinos are not photons. Neutrinos pass through matter almost as if it doesn't exist, so guiding them with optic fibre or anything else is a non-starter. I don't see why you think this would have simplified the experiment.

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Coat

A new dataset is expected by the end of November

November?! I thought these things were moving faster than the speed of light?

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Joke

November 30th, 1492

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Happy

Bring it on...

This is ALL fantastic stuff.

The more accuracy, the better.

Physics. The FULL understanding of which is what EVERYTHING is made of...

Chemistry...

Biology...

It's all physics really...

Possibly...

Oh, and philosophy... :o)

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Boffin

In the same way that...

all [electronic] computing is toggling voltage levels. Just because you know the complete CPU instruction set, it doesn't mean you understand an XML schema or machine vision. A list of fundamental particles doesn't tell you about the elegance of the extended phenotype of a caddisfly larvae.

Still, fantastic stuff about the bottom layer.

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Anonymous Coward

Re: Bring it on

"It's all physics really... Possibly..."

Possibly not: http://xkcd.com/435/

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Actually...

It's the best guess at an explanation of the things that we observert are made of.

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Big Brother

Movember

They're going to measure how neutrinos will be affected by the moustaches being grown.

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Pint

@Richard French

Not sure what you mean by a fibre optic loop. Neutrinos are not photons, and wouldn't be carried by a fibre-optic loop. They would pass through it completely, the same as they do through the entire planet. There is nothing known that can reflect them either. Using fibre optics wouldn't even work for a speed test with light, as the velocity of the photons would be changed by the fibre optic medium I believe, complicating the calculations.

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Igor!

Igor! The Swit...

Oh, you have already, already.

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Coat

Yeth, marther!!

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Boffin

To Richard French

Neutrinos are seriously hard to direct - from Cern they simply aimed directly at Grand Sasso through the earth - and they went through without a problem - further reading will tell you they are so good at slipping through stuff they receiver at Grand Sasso is solid lead and only records an occasional impact,

So it is much like light going throuh space on a tiny scale - as far as a neutrino is concerned the occasional atom nucleus is so far from the next that a collision is very rare. Furthermore a neutrino does not carry any charge (AFAIK - correct me if I am wrong) so it does not easily get diverted by electrons or protons.

If you sent it down a fibre optic it would simply go straight out at the first bend.

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FAIL

Enough already ....

I didn't know HOW naive I was .... thanks for all the replies - I did have the whole thing A about T

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Happy

And more.....

It's A about F, or A over T. (It's your day for corrections isn't it?)

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@Richard French

Think yourself lucky - I asked more or less the same thing on a previous related article, but received a single thumbs down and no explanations!

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FAIL

I Say Measurement Error

Very much like "Cold Fusion" and all the perpetual energy generators out there.

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Anonymous Coward

What about the *other* part of Richard's question?

Ok, so we know that neutrinos won't follow a loop, but even if they could you would have another problem. In order to get any kind of accurate measurement you would need to have a decent sized loop*. As soon as you have a decent sized loop all the other problems related to a moving** frame of reference come back into play and you would have to try to compensate for the effects around the whole loop***.

* A small loop would have the problem of "how many times has that neutrino been around?

** Earth revolving and orbitting.

*** Which unfortunately are unlikely to add up to a net zero.

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Alert

Igor we need more Igor's

If CERN doesn't have an Igor on staff and a big red switch or lever I'm going to me very dissapointed.

Lets face it, these guys are doing mad^H^H^H MAD science.

Wild haired white-coated boffins are one thing

But if you don't have an Igor or two, you just ain't doing it right :)

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This is old news

Announced 3 days ago in many other places. El Reg is running behind. Not the first time btw.

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Trollface

The delay in publication was caused by time dilation in the vicinity of superluminal neutrino beam.

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WTF?

Yeah..

It's like they get weekend off or something... WTF??

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No No No

Ell Reg is on Standard Relativistic Time, every one else reporting this is on Neutrino Time.

That's why the clocks went back over the weekend.

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This post has been deleted by its author

Could they not...

have different spacings between the pulses to correlate them better?

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Silver badge

Some pulses received

.... . .-.. .--. -- . .. .- -- - .-. .- .--. .--. . -.. .. -. .- -. . ..- - .-. .. -. --- ..-. .- -.-. - --- .-. -.--

A 1907 Coherer for Radio probably works better than any detector for Neutrinos

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Coat

"Hello ... CERN help desk.."

"What?, your neutrino experiment gave some strange results, ...... mmmm ....... have you tried turning it off and then on again ?

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Joke

Sorry but we don't serve neutrino's in here.

A neutrino walks in to a bar.

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Pint

A neutrino goes into a pub ...........

.... and not a single person notices it.

Within minutes several billion, squillion other neutrinos go into the same pub.

Once again nobody notices a thing.

Then one neutrino lepton to the bar and did a little jig, which may or may not have caught the attention of at least one person in the bar.

I blame it all on the amount of tau-killer slammers.

<did i post this twice?>

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Pint

A neutrino went into a bar ........

... and not one person noticed.

75 trillion squillion other neutrinos went into the same bar and still nobody noticed.

Then one neutrino lepton to the bar and did a little jig, which may or may not have been noticed by at least one or more peeps in the bar, but who can tell?

I blame it all on those tau-quila slammers.

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